Blast burner nozzle



Sept. 1944- E. J. HAEDIKE BLAST BURNER NOZZLE Filed Jan. 16, 1941 10 Imvamm'o [cl ward Q2 CJ-(aed/Xze 4W 14 Qqrrowxs Patented Sept. 5, 1944BLAST BURNER NOZZLE Edward J. Haedike, Chicago, Ill., assignor toNational Machine Works, Chicago, 111., a corporation of IllinoisApplication January 16, 1941, Serial No. 374,715

2 Claims.

The invention relates to nozzles for blast burners such as are used forthe combustion of high pressure mixtures of gaseous fuel and. air. In

such high pressure or blast burners, the velocity I of the gas-airmixture, discharging from the burner, so far exceeds the'normal rate offlame propagation as to make it essential to provide some meansassociated with the burner nozzle for stabilizing the ignition point ofthe flame.

Otherwise, so-called blow-off will occur or, even worse, if the furnacetemperature is below the ignition temperature for the gas-air mixture,ignition may not occur at all, with the result that the furnace or thelike is filled with dangerously explosive mixture of gas and air.

Though various expedients have heretofore been used for preventingblow-off in blast burner nozzles of the type indicated, all of them havesome one or more objectionable characteristics. For example, many ofthem entail the use of a pocketed baiile to confine a fringing orpiloting flame, supplied with a suitable gas-air mixture. With such apocketed baffle arrangement there i a tendency to retain products ofcombustion in the vicinity of the ignition zone, but any such retentiondefeats the whole purpose of the arrangement since carbon dioxide is oneof the best of all inhibitors of combustion for gas-air mixtures,Similarly, if the fuel is a big hydrogen content gas, which isrelatively fast burning, the ignition and combustion of the pilotingfringe in the pockets defined by the bafiie may, in many instances,produce local temperatures so severe that they will damage or destroyadjacent portions of the nozzle. 7

The general aim of the present invention, is to overcome the defectsnoted with respect to the prior devices, and to afford a blast burnernozzle which is characterized not only by its ability to maintaincombustion without blowing, under even high supply pressures, but whichalso has great durability under even extremely severe conditions ofusage.

More specifically, it is an object of the invention to provide a nozzleof the class indicated embodying a bafiie arrangement defining a shortcombustion tunnel or chamber which coacts in a novel manner with themain port and fringingflame ports, of the nozzle, to assure stability ofcombustion under a wide variety of gas-air pressure conditions.

' is to be understood that I do not thereby intend- Figure 1 is an endview, taken from the outer end, of a blast burner nozzle embodying theinvention.

Fig. 2 is a longitudinal sectional view of the nozzle, takensubstantially along the line 22 in Fig. 1.

While the invention is susceptible of various modifications andalternative constructions, I' '1 have shown in the dawing and willherein de-' scribe in detail'the preferred embodiment, but it to limitthe invention to the specific form disclosed, but intend to cover allmodifications and alternative constructions falling within the spiritand scope of the invention as expressed in the appended claims.

In the instant embodiment of the invention,

the nozzle shown comprises a cast metal body 10' "through which amixture of combustible gas and air is supplied under pressure. Thechamber ll tapers longitudinally inward and terminates in a main port orthroat [4 formed in a frustoconical eminence IE on the outer end of thebody H].

It will be observed that the port I4 is of large "from it at highvelocity, in fact at a velocity well Further objects and advantages ofthe invencross sectional area to accommodate a large volume of gas-airmixture, and it is so dimensioned, relative to the shape and dimensionsof the supply passage il, that the gas-air mixture issues in excess ofthe normal rate of flame propagation for the mixture.

To form a stabilizing fringe of flame circumferentially about the mainport M, a plurality of auxiliary ports l6 are led from the supplychamber I I. These ports is are of small or restricted cross section ascompared to the main port I4.

To form a combustion chamber or recess H in the end of the burner body,an annular bafile ring i8 is provided, being formed, in the presentinstance, as an integral part of the body ID. One key feature of thecombustion chamber shape is that its inner side walls'are contoured soas to converge inwardly, smoothly, to an end opening l9 which is ofsmaller diameter than the inner end of the chamber although slightlylarger than the diameter of the main port It. As to the smooth contourof the inner face of this chamber l'i, observe particularly that it isentirely free of any undercuts or pocketing. Furthermore, the root ofthe groove, defined between the eminence This chamber has an open outerl5 and the baffie ring I8, is smoothly curved so that there is also nopocketing or undercutting in that area. In other words, the opposed sidefaces of the eminence l5 and baffie .IS merge smoothly in the root ofthe groove between them. As a consequence, there is no undercut orpocket which could trap products of combustion.

It is also to be observed that the auxiliary ports I6 slant outwardly,from the longitudinal center line of the body l0, toward the curvedinner face of the ballie I8. Accordingly, the small streams of gas-airmixture emerging from the .ports I B sweep or scrub out along the innerface of the baffle as they burn and are bent inward, by the curvature ortaper of the baffle face, toward the main body of gas-air mixture,streaming from the large port I4.

On the other hand, the high velocity gas-air' mixture issuing from themain port l4 converges slightly, forming a vena contracta about an inchfrom the mouth of the port I4. The outer portion of the issuing pencilof gas-air mixture from the main port is thus ignited by the surroundingfringe of flame from the ports I6, the latter being slowed down by thescrubbing action on the inner face of the baffle ring I6, as heretoforenoted. This results in a temperature within the combustion chamber I! ofthe order of 2800 F. The high velocity main jet burns progressivelyinward and forward from the face of the burner. It will thus be seenthat the piloting fringe of flame creates a temperature within thechamber I! which stabilizes the base of ignition of the main jet, andaccordingly, blowing of the flame away from the nozzle is obviated. Infact, the present nozzle is capable of utilizing, without blow-off,gas-air mixtures at in excess of seventy per cent greater pressures thancan be similarly accommodated in many prior nozzles designed for flameretention.

Not only is the mixture effectually ignited and the flame stabilized,but in addition a free exit for the products of combustion is afforded.Though the contour of the baffle confines the fringing flames (from theports I6) in a lateral direction and causes them to converge inwardlytoward the main stream of fuel, it does not pocket or positively confinethem, or their products of combustion, against final escape.

Also of note is the massive character of the baffle ring l8 in its outerportion, this being accompli'shed in part by the very shape of its innersurface. This thickness of metal in the outer edge of the baffle ringmakes it possible to cast the nozzle from low cost gray iron, asdistinguished from high cost heat-resistant alloys, because of the highrate of heat dissipation accomplished. This is a matter of vitalimportance in many installations in achieving a long useful life for thenozzle. It is often impractical in furnace installations to protect thenozzle from radiant heat reflected from the furnace structure directlyinto the mouth of the nozzle. In the absence of special precautions,this heat is likely to prove extremely damaging to the nozzle. Thestructure of the present bafile ring 18 is such, however, as to afford ahigh enough rate of dissipation for the reflected heat, that the nozzletemperature does not build up to a dangerous value. Endurance tests haveproved the present nozzle to be capable of withstanding furnacetemperatures ranging upward from 2500 F. during many hours of service,while other prior nozzles broke down under the same conditions afterless than an hour of service.

From the foregoing, it will be seen that a very effectual, long-lifedevice has been provided. It is, however, one which is extremely simpleand economical to manufacture.

I claim as my invention:

1. A blast burner nozzle comprising a metal body portion having apassage extending longitudinally therethrough, said passage beingprovided with an annular constriction intermediate its ends, the saidpassage on the approach side of said constriction tapering uniformlyfrom a large inlet to a main port of reduced cross sectional areadefined by and extending through said constriction, the discharge end ofsaid main port opening into an enlarged terminal portion of said passagewhich opens through the end of said body in a discharge orifice greaterin cross sectional area than said main port, said passage enlargementbeing generally circular in cross sectional outline and defined by acircumscribing smoothly curved wall which gradually expands rearwardlyfrom said discharge opening to a point rearwardly of the discharge endof said main port to form an annular roove in said constrictioncircumscribing the discharge end of said main port, and a plurality ofducts communicating with said passage rearwardly of said constriction,said ducts being inclined outwardly from the axis of said passage in thedirection of fluid flow through said ducts, and discharging into saidannular groove, the discharge ends of said ducts terminating at the baseof said curved wall and being positioned to direct said fluid upon thecurved wall surface of said enlarged terminal portion of the passage atpoints rearwardly of the discharge end of said main port.

2. A blast burner nozzle described in claim 1, wherein the wall of thenozzle from the region of the bottom of said groove to the discharge endof the nozzle gradually increases in thickness to provide a mass ofmetal for affording a high rate of heat dissipation.

EDWARD J. HAEDIKE.

